1. Field of the Invention
The present invention relates to a microwave oven, and more particularly to a food amount detector capable of automatically detecting the amount of food placed in the microwave oven, and to the microwave oven employing a food amount detector and a control method thereof.
2. Description of the Prior Art
Generally, a microwave oven heats/cooks the food by microwave. Such a microwave oven comprises a high voltage transformer and a magnetron. The high voltage transformer transforms common voltage (220V/110V) into high voltage for driving the magnetron which generates the microwave of a predetermined degree of high frequency. In such a situation, the microwave vibrates the water molecules in food, so that the food is cooked by friction heat produced due to the vibration of water molecules.
FIG. 1 is a partial cutaway perspective view of a general microwave oven. In FIG. 1, reference numeral 1 designates a body, 2 is a cooking chamber, 3 is a device chamber, 4 is a door, 5 is a rotational plate, and 6 designates a cover. The inner space of the body 1 is divided into a left and a right space in which a cooking chamber 2 and a device chamber 3 are respectively defined. Electric devices are installed in the device chamber 3. A cover 6 encases the body 1, thereby forming the appearance of the microwave oven. A door 4 is pivotally fixed to one side of the body 1, to open/close the front side of the cooking chamber 2. A rotational plate 5 is disposed at the bottom surface of the cooking chamber 2, and the food to be cooked is placed thereon. The rotational plate 5 is rotated by a driving motor (hereinafter referred to as DM; see FIG. 2) which is installed on the lower surface thereof. Additionally, reference numeral 7 designates a front panel, 8 is an air guide, 9 is a cooling fan, HVT is a High Voltage Transformer, HVC is a High Voltage Condenser, HVD is a High Voltage Diode, and MGT designates a Magnetron. Those are installed in the device chamber 3. The high voltage transformer HVT transforms the common voltage 220V/110V into high voltage 2000V. The high voltage 2000V is doubled to 4000V by the high voltage condenser HVC and the high voltage diode HVD. The magnetron MGT is driven by such doubled voltage 4000V to generate a microwave of 2450MHz. The cooling fan 9 blows air into the device chamber 3 to cool the heated electric devices installed therein such as the magnetron MGT, high voltage transformer HVT, or the like. The air guide 8 is installed near the magnetron MGT, to guide air which has been heated while the magnetron MGT is cooled, into the cooking chamber 2. The front panel 7 is installed at the front surface of the device chamber 3. The user inputs the data of his selected keys into the microwave oven, and his selections for driving the microwave oven are displayed on the front panel 7.
FIG. 2 is a schematic block diagram of FIG. 1. In FIG. 2, reference numeral 10 designates a noise filter, 20 is a driving section, 30 is a microwave generator, 40 is a control section, 50 is a input section, and 60 designates a display section. An input section 50 inputs the signals of the user""s selections into a control section 40. A plurality of function keys 51 are provided in the input section 50. Here, the function keys are for respective driving conditions of the microwave oven. More specifically, there could be the function keys for adjusting cooking temperature, cooking time, level of the microwave energy, or the like as the user wishes. In addition, there could be the function keys for selecting the automatic cooking process, in which the user inputs the data about the amount of the food so that the food is automatically cooked in accordance with the cooking data which were preset therefor. The display section 60 displays the driving conditions of the microwave oven. Here, the input section 50 and the display section 60 are preferably provided at the front panel 7 shown in FIG. 1. The driving section 20 comprises driving motors DM and FM for respectively driving the rotational plate 5 and the cooling fan 9. Further, the driving section 20 comprises relay switches RS1 and RS2, respectively for supplying the driving power to the high voltage transformer HVT and the driving motors DM and FM. Accordingly, when the relay switches RS1 and RS2 of the driving section 20 are turned on, the driving power is supplied to the high voltage transformer HVT and the driving motors DM and FM. A general microcomputer would serve as the control section 40. The control section 40 properly controls the driving conditions of the microwave oven by selectively turning on/off the relay switches RS1 and RS2 of the driving section 20. The control section 40 also sends the signals to the display section 60 and displays such driving conditions of the microwave oven. The high voltage transformer HVT transforms the common voltage supplied from the driving section 20 into high voltage, and transmits the high voltage to the microwave generator 30. The microwave generator 30 comprises the high voltage condenser HVC, the high voltage diode HVD, and the magnetron MGT. The microwave generator 30 is driven by high voltage supplied from the high voltage transformer HVT, just as it was described above with respect to FIG. 1. The noise filter 10 receives the driving power, and transmits the driving power to the driving section 20. Further, the noise filter 10 prevents feed back of high frequency wave generated from the microwave generator 30 toward an input line.
Operation of the conventional microwave oven constructed as above will be described below. First, the user pulls the door 4 of the body 1 and opens the cooling chamber 2. Then, the user places the food to be cooked on the upper surface of the rotational plate 5. Next, the user closes the door 4, and selects cooking conditions of microwave oven by selecting function keys 51 of the input section 50 which is provided at the front panel 7. By selecting the function keys 51, the user sets the cooking time, temperature, and level of the microwave energy as he guesses proper for the amount of the food placed in the microwave oven. In addition to such a manually-selected driving condition, there may be an automatically-selected driving condition in which the user simply selects keys provided for the food he/she is preparing and the amount thereof, so that the food is cooked in a manner which was preset in the microwave oven. Accordingly, the input section 50 inputs the signals from the selected keys to the control section 40, and the control section 40 drives the driving section 20 in accordance with the user""s selections. More specifically, the control section 40 turns on the relay switch RS1 so that the power is supplied to the high voltage transformer HVT. Accordingly, the high voltage transformer HVT transforms the common voltage 220V/110V into high voltage. And the high voltage condenser HVC and the high voltage diode HVD double the high voltage to 4000V, and supply the same to the magnetron MGT. The magnetron MGT is driven by such doubled high voltage 4000V to generate the microwave of 2450 MHz. Then microwave is radiated into the cooking chamber 2 so that the food is cooked. Further, the control section 40 simultaneously turns on the relay switches RS1 and RS2 so that the control section 40 drives the driving motors DM and FM, respectively. Accordingly, the rotational plate 5 of the cooking chamber 2 is rotated so that the microwave is uniformly radiated to the food. In this situation, the cooling fan 9 of the device chamber 3 blows air into the device chamber 9, to cool the electric devices such as the high voltage transformer HVT, the magnetron MGT, the high voltage diode HVD, and the high voltage condenser HVC, etc. Here, the control section 40 turns on/off the relay switch RS1 regularly, to control the driving conditions of the magnetron MGT. Accordingly, the level of the microwave generated from the magnetron MGT are properly adjusted, so that the food in the cooking chamber 2 is appropriately cooked under the selected driving conditions.
Meanwhile, in addition to the manually-selected driving conditions, the conventional microwave oven further has an automatically-selected driving condition. With such an automatically-selected driving condition, however, the amount of the food can not be determined by the microwave oven. Accordingly, the user has to guess the best cooking mode for the food, and based on his/her guess, one selects corresponding function keys, and the microwave oven cooks the food in accordance with-such inputted data. Here, when the food requires more time or greater level of microwave energy for cooking than the user inputted, the food is under-cooked. Likewise, when the food requires less time, or less level of microwave energy for cooking than the user inputted, the food is overcooked. Accordingly, in order to cook the food appropriately, it is important that the user may judge the exact amount of the food and drive the microwave oven accordingly.
The conventional microwave oven, however, can not offer the solution to the above-mentioned problem, since the user has to guess the amount of the food. Further, in the event that there is no function keys for the amount of the food the user wishes to cook, the user has to manually input the data for cooking time, level of microwave energy, etc., so that the preparation of the food becomes inconvenient and complex.
Further, when using a conventional microwave oven, since the user has to guess the amount of the food he/she is preparing, the preciseness of the food amount is not guaranteed, so that the cooking operation may be inappropriately performed. If the user selects an improper function key by his/her mistake or misjudgement, the food can be overcooked, or under-cooked. Thus, the food can not be appropriately cooked.
There has been a solution suggested for the above-mentioned problem such as a gas sensor, a weight sensor, etc. which could be employed in a microwave oven to determine the amount of the food. However, since these devices are expensive and require a rather complex manufacturing process, the manufacturing cost is increased, and the efficiency is accordingly deteriorated.
Accordingly, the present invention has been made to overcome the above-mentioned problem of the prior art, and the first object of the present invention is to provide a food amount detector for a microwave oven capable of automatically determining the amount of the food, and microwave oven employing such a food amount detector and control method thereof.
The second object of the present invention is to provide a food amount detector capable of setting exact data for driving conditions of the microwave oven in accordance with the amount of the food and appropriately cooking the food, and also to provide the microwave oven employing such a food amount detector and control method thereof.
The third object of the present invention is to provide a food amount detector made of parts having reasonable prices so that the manufacturing cost can be minimized and the efficiency can be improved, and also to provide a microwave employing such a food amount detector and control method thereof.
The first feature of the food amount detector according to the present invention is that output voltage of the microwave generator is detected, so that the amount of the food placed in a cooking chamber of the microwave oven is determined based on such detected output voltage of the microwave generator.
The second feature of the food amount detector according to the present invention is that it comprises a voltage detector for detecting output voltage of a magnetron, and a control means for determining the amount of the food placed in the cooking chamber of the microwave oven based on the output voltage of the magnetron which is detected by the voltage detector. The voltage detector comprises at least one voltage dividing resistor connected to a cathode of the magnetron to divide the output voltage of the magnetron, so as to detect the voltage divided at a predetermined ratio by the voltage dividing resistor and then outputted. The current is converted into the plus (+) current while the bias voltage is applied to one side of the voltage dividing resistor, and the voltage detector inputs such converted plus (+) current to the control means. The current is converted into the plus (+) current while a reversion amplifier is connected to one side of the voltage dividing resistor, and the voltage detector inputs such converted plus (+) current to the control means. The control means comprises a comparison/determination part for determining the amount of the food by receiving the output voltage of the magnetron, which is detected by the voltage detector for a predetermined time, and by comparing voltage variation per predetermined time unit with a reference voltage variation which was pre-inputted.
The third feature of the food amount detector of a microwave oven according to the present invention is that it comprises a voltage detector for detecting respective output voltages of a magnetron and a high voltage transformer, and a control means for determining the amount of a food placed in a cooking chamber of a microwave oven based on the respective output voltages detected by the voltage detector. The voltage detector comprises at least one voltage dividing resistor connected to a cathode of the magnetron to divide the output voltage of the magnetron, and a step-down resistor connected to a ground of the high voltage transformer, so as to detect the voltages Vb and Va, respectively, in which the voltage Vb is that which is divided at a predetermined ratio by the voltage dividing resistor and then outputted, and the voltage Va is that which is outputted from the voltage dividing resistor. The current is converted into the plus (+) current, while the bias current is applied to one side of the voltage dividing resistor, and the voltage detector inputs such converted plus (+) current to the control means. The current is converted into the plus (+) current, while a reversion amplifier is connected to one side of the voltage dividing resistor, and the voltage detector inputs such converted plus (+) current to the control means. The control means comprises a calculation part for receiving a plurality of output voltages detected by the voltage detector, and for calculating an impedance and a cutoff voltage through the output voltages, and a comparison/determination part for determining the amount of the food by comparing values of impedance and the cutoff voltage obtained by the calculation part with data about the impedance and the cutoff voltage which are pre-inputted.
The first feature of a microwave oven according to the present invention is that the microwave oven comprises a voltage detector for detecting output voltage of a magnetron, a control means for determining the amount of the food placed in a cooking chamber of the microwave oven based on the output voltage of the magnetron which is detected by the voltage detector, and a driving means for driving the mgnetron in accordance with the amount of the food which is determined by the control means, and for cooking the food under the appropriate conditions. The voltage detector comprises at least one voltage dividing resistor connected to a cathode of the magnetron to divide the output voltage of the magnetron, so as to detect the voltage which is divided at a predetermined ratio by the voltage dividing resistor and then outputted. The control means comprises a comparison/determination part for determining the amount of the food by receiving the output voltage of the magnetron, which is detected by the voltage detector for a predetermined time, and by comparing the voltage variations per predetermined time unit with the reference voltage variation which is pre-inputted, and a driving control part for controlling the driving means in accordance with the amount of the food which is determined by the comparison/determination part.
The second feature of the microwave oven is that the microwave oven comprises a control means for determining a amount of a food placed in a cooking chamber of a microwave oven based on output voltage of the magnetron which is detected by the voltage detector, and a display means for displaying the data about the amount of the food which are determined by the control means. The control means comprises a comparison/determination part for determining the amount of the food by receiving the output voltage of the magnetron, which is detected by the voltage detector for a predetermined time, and by comparing the voltage variations per predetermined time unit with the reference voltage variation which is pre-inputted, and a display control part for controlling the display means in accordance with the amount of the food which is determined by the comparison/determination part.
The third feature of the microwave oven according to the present invention is that the microwave oven comprises a voltage detector for detecting output voltage of a magnetron, a control means for determining the amount of a food placed in a cooking chamber of a microwave oven based on output voltage of the magnetron detected by the voltage detector, a driving means for properly cooking food by driving the magnetron in accordance with the amount of the food which is determined by the control means, and a display means for displaying the data about the amount of the food which is determined by the control means.
The fourth feature of the microwave oven according to the present invention is that the microwave oven comprises a voltage detector for detecting respective output voltages of a magnetron and a high voltage transformer, a control means for determining the amount of a food placed in a cooking chamber of a microwave oven based on a plurality of output voltages of the microwave generator which are detected by the voltage detector, and a driving means for properly cooking food by driving the microwave generator in accordance with the amount of the food which is determined by the control means. The voltage detector comprises at least one voltage dividing resistor connected to a cathode of the magnetron to divide output voltage of the magnetron, and a step-down resistor connected to a ground of the high voltage transformer, so as to detect output voltages Vb and Va, respectively, in which the output voltage Vb is that which is divided at a predetermined ratio by the voltage dividing resistor and then outputted, and the output voltage Va is that which is outputted from the step-down resistor. The control means comprises a calculation part for receiving a plurality of output voltages detected by the voltage detector, and for calculating an impedance and a cutoff voltage of the microwave generator, a comparison/determination part for determining the amount of a food by comparing values of impedance and the cutoff voltage obtained by the calculation part with data about the impedance and the cutoff voltage which are pre-inputted, and a driving control part for controlling the driving means in accordance with the amount of the food which is determined by the comparison/determination part.
The fifth feature of the microwave oven according to the present invention is that the microwave oven comprises a voltage detector for detecting respective output voltages of a magnetron and a high voltage transformer, a control means for determining the amount of a food placed in a cooking chamber of a microwave oven based on a plurality of output voltages of the microwave generator which are detected by the voltage detector, and a display means for displaying the data about the amount of the food which are determined by the control means. The control means comprises a calculation part for receiving a plurality of output voltages detected by the voltage detector, and for calculating an impedance and a cutoff voltage of the microwave generator, a comparison/determination part for determining the amount of a food by comparing values of impedance and the cutoff voltage which are obtained by the calculation part with data about the impedance and the cutoff voltage which are pre-inputted, and a display control part for controlling the display means in accordance with the amount of the food which is determined by the comparison/determination part.
The sixth distinguishing feature of the microwave oven according to the present invention is that the microwave oven comprises a voltage detector for detecting respective output voltages of a magnetron and a high voltage transformer, a control means for determining the amount of a food placed in a cooking chamber of a microwave oven based on a plurality of output voltages of the microwave generator which are detected by the voltage detector, a driving means for properly cooking food by driving the microwave generator in accordance with the amount of the food which is determined by the control means, and a display means for displaying the data about the amount of the food which are determined by the control means.
The feature of a method for controlling a microwave oven according to the present invention is that the control method comprises steps of detecting output voltage of a magnetron, determining the amount of a food placed in a cooking chamber of a microwave oven based on an output voltage of the magnetron which is detected in the voltage detecting step, and cooking food properly by driving the magnetron in accordance with the amount of the food which is determined in the food amount determination step. The amount of the food is determined in the food amount determination step by receiving the output voltage of the magnetron detected in the output voltage detection step for a predetermined time, and comparing the voltage variation per predetermined time unit with reference voltage variation which is pre-inputted. The food amount determination step comprises sub-steps of inputting output voltage variation per predetermined time unit detected in the voltage detection step to a Neural Net Program after the voltage variation is converted into patterned values having a predetermined law therein, outputting results from the Neural Net Program after calculating equations of the Neural Net Program referring to pre-inputted patterned values and pre-leamed data, and determining the amount of a food placed in a cooking chamber of a microwave oven based on the output result. The amount of a food is determined in the food amount determination step by receiving a plurality of output voltages which are detected in the voltage detection step, calculating values of impedance and cutoff voltage with the output voltages, and by comparing the values of impedance and cutoff voltage with data of the impedance and the cutoff voltage which are pre-inputted. The food amount determination step further comprises a sub-step of displaying the data about the amount of a food which are determined in the food amount determination step.
Accordingly, since the amount of the food is automatically determined by the microwave oven, and the food is cooked under the appropriate driving conditions of the microwave oven, the user finds it convenient in using the microwave oven, and mistakes of the user in handling the microwave oven are prevented. Also, since the parts are inexpensive, the manufacturing cost is reduced, and the manufacturing process becomes simplified, so that the productivity is increased.